The invention relates generally to imaging systems and more particularly to an image registration system and method adapted for use in medical imaging systems.
Typically imaging systems such as X-ray systems, computed tomography (CT) systems, positron emission tomography (PET) systems and the like are used to acquire images of various parts of a subject. The images generated by the imaging system are analyzed using imaging algorithms and pathologies of concern are highlighted which are then reviewed by radiologists for final diagnosis. In order to facilitate accurate diagnosis, it is usually important to generate high quality images with minimum image degradation.
There are several reasons for degradation in images generated by such imaging systems. Such degradation is usually related to the portion of the anatomy that is being imaged. For example, respiratory motion during image acquisition is one major source of degradation of positron emission tomography (PET) and computed tomography (CT) images of the thorax and the upper abdomen.
As a result of such motion blurring, feature location such as tumors, volume, and its contrast with surrounding tissue is often inaccurately estimated. Such inaccurate estimation often leads to incorrect tumor localization, staging, radiation therapy planning, and treatment monitoring.
One method that is often employed to limit motion blurring is active breath control. However, performing active breath control may become very uncomfortable and almost impossible for patients with serious illness. Another technique known as the gated PET/CT technique allows for estimation of respiratory motion from gated CT acquisitions and then used for motion compensation during PET image reconstruction. Typically, motion estimation is performed using spline-based transformations, demons algorithm and other optical flow based algorithms. However, such techniques are time consuming and often require additional circuitry, which in turn increases the overall cost of the system.
Therefore, what is needed is a simple, fast and accurate method and system for estimating motion from gated CT acquisition for use in PET image reconstruction.